Autism spectrum disorders and the visual analysis of human motion

Appropriate social behavior requires a fine-tuned ability to perceive other people’s actions. Human movement is a rich source of social information. The ways in which people move tell us volumes about their intentions and emotions. Maggie Shiffrar and her colleagues at Rutgers University in New Jersey set out to determine how, and how well, people with autism perceive human movement.

The researchers conducted a series of psychophysical experiments to address this question, and found that people with autism differ from typical observers in their visual sensitivity to human movement. Whereas typical observers show greater visual sensitivity to human motion than to moving objects or animals, observers with autism do not show this preference. Shiffrar’s second question was why: What is the mechanism underlying this difference?

One clue is that typical observers are more visually sensitive to the presence of angry human motion than they are to happy, sad or fearful human motion, indicating that emotional processes are linked to normal visual analyses of human movement. Thus, differences in emotional processing may account for some of the differences between typical observers and those with autism. Another hypothesis involves the motor system.

When typical observers view moving people, neural activity increases in both the visual and motor systems of the observer. When the researchers tested individuals on the autism spectrum for motor ability and visual sensitivity to various types of displays, they found a significant association between motor ability and visual sensitivity to human movement. This suggests that compromised motor abilities may in turn lead to compromised visual sensitivity to other people’s motor actions.

In conclusion, the results from Shiffrar’s lab suggest that people on the autism spectrum struggle to see socially relevant information, such as the actions of other people. Thus, they experience deficits not only in their social abilities but also in their perceptual abilities when watching other people move.